1. Field of the Invention
The present invention relates to an adhesive system of an α-cyanoacrylate adhesive composition.
More precisely, the present invention relates to an adhesive system of an α-cyanoacrylate adhesive composition used with a plastic container, a plastic nozzle, a plastic cap, or a plastic tube to convey the adhesive composition to the nozzle. The adhesive has an excellent fast setting property and excellent storage stability, and can be preferably used for the adhesion of difficult to adhere materials such as acryl resins, chrome plating, nickel plating, FRP, Bakelite, thermoplastic elastomers (hereinafter, abbreviated as TPE) EPDM rubbers and the like, and porous materials such as papers, woods, leathers, ceramics and the like.
2. Description of Related Art
α-Cyanoacrylates easily cause anion polymerization by anionic active species, such as moisture, an alkaline material or the like, in a material to be adhered, or in the air, and so they find wide application as instantaneous adhesives for rubbers, plastics, metals, glass and the like.
However, conventional α-cyanoacrylate adhesives do not have a sufficient fast setting property for the adhesion of difficult to adhere materials such as acryl resins, chrome plating, nickel plating, FRP, Bakelite, TPE, EPDM rubbers, porous materials such as papers, woods, leathers, ceramics and the like.
As a means for eliminating this defect, a method in which a hardening accelerator is added to an α-cyanoacrylate adhesive composition has been known. Various compounds have been attempted from 1975 to 1985 as hardening accelerators. For example, polyethylene glycol derivatives are disclosed in JP-A-54-28342 and calix-arenes are disclosed in JP-A-60-179482. In addition, JP-B-55-2238 discloses that crown ethers (15-crown-5-ether, 18-crown-6-ether and dicyclohexyl-18-crown-6-ether) are effective as hardening accelerators for the adhesion of porous materials such as papers, woods and the like.
On the other hand, however, another defect appeared in that the storage stability of the adhesive itself is remarkably reduced when a hardening accelerator is added to the extent where a sufficient fast setting property of a hard to adhere material is obtained.
Therefore, in order to store an α-cyanoacrylate adhesive composition containing a hardening accelerator for a long term, it is necessary to store the adhesive composition in a metal container that is completely impermeable to water, or when the adhesive composition is stored in a plastic container permeable to water, it is necessary to store it in an atmosphere controlled to a low humidity. These are very inconvenient storage problems. Even if a metal container is used, when one or both of a nozzle or a cap is made of a water-permeable plastic material such as polyethylene, polypropylene or the like, moisture permeates therethrough and thus a lowering of the storage stability cannot be avoided. For example, the moistening of the adhesive composition retained in the inside of the nozzle proceeds after applying the adhesive composition to a material to be adhered, causing rapid gelation, setting or the like. Upon the next application of the adhesive, problems arise in that the nozzle becomes blocked and the adhesive composition cannot be squeezed from the container. Nozzle clogging is frequent and has been one of great defects of the α-cyanoacrylate adhesive system. In addition, sometimes the problem arises that the entire adhesive composition in the plastic container becomes hardened and the adhesive cannot be used. Improvement in all of these respects has been earnestly demanded.
In industrial adhesive applicators, the adhesive composition is introduced to a plastic nozzle as an outlet through a plastic tube. The plastic tube is made of a water permeable material, having a narrow diameter. Also in this case, thickening, gelation or hardening due to moistening tends to occur in a tube or nozzle during interruption or use in the summer. Improvement in this respect is also earnestly demanded.
Therefore, JP-A-62-100568 proposes an adhesive composition having a fast setting property with improved stability during storage and use. The publication describes that the storage stability is improved as compared with conventional products when BF3, SO2 and 18-crown-6-ether or the like is added to 2-cyanoacrylate. Even if such an adhesive composition is used, however, when a water-permeable plastic material is used for the nozzle or other plastic parts, nozzle clogging is likely to occur and therefore a satisfactory storage stability has not been attained. In other words, an adhesive used with a water-permeable plastic material, for example a nozzle, container or the like and which has an excellent fast setting property and an excellent storage stability has never been obtained.